Architectural designs for computing devices connect internal components by a communications channel referred to as a bus. Various devices, such as integrated circuits (ICs), and devices that include ICs are typically attached to a bus that is controlled by one or more programmable microcontrollers.
A capability for detection of attached compatible devices of a computing system is typically included in computer architectural designs. This is done to improve reliability and accurately isolate error detection related to hardware attached through slots or pluggable sockets. Presence detection of devices is generally accomplished by use of a dedicated pin on the hardware interface into which the device is plugged. The dedicated pin carries a signal indicating the presence of the device when the device is attached, and the signal discontinues when the device is removed. The dedicated signal pin is typically sampled by circuit logic, which allows system management software to identify whether a device is present.
The approach of using dedicated pins for device detection incurs additional manufacturing cost of the computer system and attachable devices. Additionally, in computer system and component designs, having additional, dedicated pins and signal lines for device presence detection is a detractor to the continuous challenge of greater density and complexity of circuit design.
An example of a bus architecture designed to attach IC devices is the Inter-Integrated Circuit bus, also known as the I2C (“I-two-see”) or I2C (“I-squared-see”)-bus. The I2C bus is used to attach low-speed peripherals to a motherboard, embedded system, cellphone, or other electronic device.
ICs that are compatible with the I2C bus have an “on-chip” interface that allows them to communicate directly via the bus. The I2C bus has become a well established world standard that is implemented in over 1000 different ICs and is used in several control architectures such as System Management Bus (SMBus), Power Management Bus (PMBus), Intelligent Platform Management Interface (IPMI), Display Data Channel (DDC) and Advanced Telecom Computing Architecture (ATCA).
The I2C bus is a simple bidirectional 2-wire bus used for inter-integrated circuit control. The two wires used are a serial data line (SDA) and a serial clock line (SCL). A master/slave relationship is used for transactions between the devices and microcontrollers and devices attached to the bus are addressable, with each device having a unique assigned address.